To hide 'Proceed to checkout' button when using the minimum order amount snippet by WooCommerce- https://www.webtoffee.com/product/paypal-express-checkout-gateway-for-woocommerce/

functions.php

<?php // do not copy this line
function eh_woocommerce_available_payment_gateways($available_gateways) {
   // Set this variable to specify a minimum order value
    $minimum = 50;

    if ( WC()->cart->total < $minimum ) { 
		if(isset($available_gateways['eh_paypal_express'])){
			unset($available_gateways['eh_paypal_express']);
		}
	}
    return $available_gateways;
}
add_filter( 'woocommerce_available_payment_gateways', 'eh_woocommerce_available_payment_gateways');